If you have, for example, a v.drawFill that goes from 0 to 320 on x and from 150 to 200 on y. The drawFill will not be affected by V_SNAPTOTOP or V_SNAPTOBOTTOM. Meaning you can never have that fill along the very bottom of the screen in not aspect correct resolutions. It's because the changes to it drawing aren't performed because it's drawing it across the entire width of the screen. I think the same probably happens with a vertical drawFill too.

Example:

Code:

v.drawFill(0, 163, 320, 37, 31+V_SNAPTOBOTTOM)

Gives a result of:

Also, the top fill in that image doesn't even need V_SNAPTOTOP to be at the very top of the screen so something is wrong there as well.